Manganese redox chemistry is fundamental to biological processes at molecular, cellular and environmental scales, from antioxidant defense to oxygenic photosynthesis. Biomedically important enzymes including Mn superoxide dismutase (MnSOD), Mn catalase (MnC), and oxalate oxidase (OXO) require a catalytic manganese cofactor for their biological function, yet the molecular mechanisms involved in delivering the essential metal ion are just beginning to be studied in detail. The goal of this proposal is to advance our understanding of the biochemical mechanisms responsible for the metal-binding maturation of Mn metalloenzymes, including MnSOD. In vitro methods (including fluorescence monitored metal uptake kinetics) will be complemented by an analysis of processes and proteins required for metal binding by manganese metalloenzymes in vivo. This work is fundamental to understanding the role of manganese trafficking in human health and disease. Further, understanding the metal binding mechanism of the ubiquitous antioxidant metalloenzyme MnSOD may contribute new insight into biological defenses against oxidative stress, a key factor in aging and neurodegenerative disorders. This work may also shed light on diseases of metal homeostasis in which metal misincorporation occurs. Roles of manganese in pathogenesis will be explored through the expression and molecular characterization of manganese catalase homologs mined from the genome of a medically important microbial pathogen, the enterohaemorraghic E. coli O157:H7. Further, the role of high-valent manganese complexes in enzyme catalysis will be investigated by applying a combination of advanced spectroscopic methods and rapid kinetics to probe the active site chemistry of oxalate oxidase. PUBLIC HEALTH RELEVANCE: Manganese is an element that plays many essential roles in health and disease. One of the important aims of this proposal is to investigate how living cells specifically deliver manganese to manganese-dependent enzymes so that they can perform their biological functions, providing important new insight into processes underlying aging and neurodegenerative disorders. The role of manganese in the virulence of the foodborne pathogen, E. coli O157:H7, will also be explored, and the mechanisms of manganese catalysis will be investigated in oxalate oxidase, an enzyme that is important in clinical bioanalytical chemistry.